Meiosis

Bio 2

Murphy

What is meiosis?

the production of haploid cells with unpaired chromosomes - word means "to diminish".

It does two things:

1. it takes a diploid cell and makes copies of cells that are haploid

2. it scrambles the specific forms of each gene that each of the gametes (sperm & egg) receive.

Key points of Meiosis

a. The process results in 4 daughter cells

b. Daughter cells are haploid

c. Daughter cells have unique combinations of chromosomes

d. Daughter cells do not have homologous pairs

e. Creates gametes (eggs & sperm)

f. Ensures variability in offspring

g. Gametes combine to create a zygote (2N) – process of sexual reproduction

Gametes: egg & sperm – each is haploid

Egg is fertilized creating a zygote

If the each gamete were n (23 chromosomes) what is 2n?

Sexual Reproduction

Overview of Meiosis -- occurs in

two stages Meiosis I and Meiosis II

Why scramble the genes?

A: It is good for genetic diversity.

How is it accomplished?

Through independent assortment and crossing-over.

What does this mean?

Why scramble the genes? The scrambling of genes is good for genetic

variation.

Crossing over: occurs when a section of chromosomes changes place with a section of its homologous chromosome.

Why scramble the genes?

Independent assortment:

depending on how the chromosomes arrange themselves during metaphase I, the cells formed can have a variety of different chromosome combinations.

The Phases of Meiosis